#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long long int k) {
    long long int sum=0;
    long long int s=(k*(k-1))+1;
    while(k--){
        sum+=s;
        s+=2;
    }
    return sum;
}

int main() {
    long long int k;
    cin >> k;
    long long int answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}